We have followed up on our findings that showed the presence of certain receptors in the immune cells of the lamina propria in the gut. We have extended the studies to biopsies from human stomach and duodenum and experimental conditions in the rat. We found that the presence of the receptors studied (Histamine2, gastrin and muscarinic receptors) is very similar between rats and human. We have studied several methodical problems and worked out modification of the in situ hybridization method so that it can be used in immune cells without the problems that made it difficult to evaluate results quanti~tatively. We found that there is an artificial amplification of the autoradiographic signal in cells with a large amount of oxidative enzymes (phagocytic cells) and that this can be prevented. We have studied the distribution of a recently cloned peptide receptor in the rat CNS (GIP or gastric inhibitory polypeptide receptor). We have found that the GIP receptor has a very unique localization suggesting that it may have a role in regulating blood pressure and limbic functions. We have also mapped its peripheral distribution, and found it present in many vascular endothel cells supporting its likely involvement in the regulation of blood flow~blood pressure.